A fecha del 11 de febrero 2025, la Agencia Espacial Europea estim\u00f3 que la roca espacial tiene un 2 por ciento\u00a0de probabilidades de chocar con la Tierra el 22 de diciembre de 2032.<\/p>\n
Rachel Feltman:\u00a0<\/b>For\u00a0Scientific American<\/i>\u2019s\u00a0Science Quickly,<\/i>\u00a0I\u2019m Rachel Feltman.<\/p>\n
Have you heard that an asteroid might\u2014just maybe\u2014smack into Earth sometime in the next few years? The rumors are true, though perhaps not as frightening as you might think. The fact is that this asteroid, called 2024 YR4, is both literally and figuratively a moving target. As of February 11, the European Space Agency\u00a0estimated that the space rock has a 2 percent<\/a>\u00a0chance of colliding with Earth on December 22, 2032. That\u2019s slightly higher than the risk you\u2019ll hear quoted in the episode that follows because we recorded it last week. Why are those numbers changing so quickly? We promise this isn\u2019t a matter of the risk going higher and higher\u00a0 \u00a0 \u00a0 as time goes on. It\u2019s a lot more complicated than that.<\/p>\n Here to explain what\u2019s going on with this potentially hazardous asteroid is Lee Billings, a senior editor covering space and physics for\u00a0Scientific American<\/i>.<\/p>\n Lee, thanks so much for coming on to chat.<\/p>\n Lee Billings:<\/b>\u00a0It\u2019s my pleasure, as always, Rachel.<\/p>\n Feltman:<\/b>\u00a0So there\u2019s an asteroid with a very low chance of hitting us. Why did this make such a big splash in the news?<\/p>\n Billings:<\/b>\u00a0So it made such a big splash in the news because, apparently, a 1 percent or greater chance of being struck by an asteroid is actually\u00a0 a big deal. And that\u2019s what this thing is. It\u2019s, it\u2019s called 2024 YR4\u2014really rolls off the tongue. It was discovered on December 27 by astronomers using the Asteroid Terrestrial-Impact Last Alert Sy stem, or ATLAS, which is a telescope in Chile. W\u00a0 hen it was roughly about two times farther out than our moon, it was zooming right by our planet, and folks were able to look at its orbit, which they\u2019re still piecing together, and determined that it was gonna make another\u00a0especially<\/i>\u00a0close pass on December 22, 2032.<\/p>\n Feltman:<\/b>\u00a0Mm.<\/p>\n Billings:<\/b>\u00a0And at that time it had about a 1.3 percent chance of striking our planet.<\/p>\n Feltman:<\/b>\u00a0Got it. So how did we detect this? You mentioned ATLAS, but tell me more about what that telescope does and whose job it is to keep an eye out for these asteroids.<\/p>\n Billings:<\/b>\u00a0Last I counted there\u2019s somewhere between a half dozen and a dozen wide-field survey telescopes that look at the sky every night, and what they\u2019re looking for is moving objects. What do we mean by moving? Everything\u2019s moving. We\u2019re looking for objects that seem to move against the background of the more distant stars, which don\u2019t seem to move \u2019cause they\u2019re so far away. You can do that by comparing images to each other over time\u2014image A, image B; image A, image B\u2014and you can see a difference, an offset in, in some little point of light. And that\u2019ll tell you: that thing\u2019s moving.<\/p>\n Most of the time, when they see these things, they know what they are; they\u2019re already cataloged. They can quickly refine their orbit, figure out what it is\u2014\u201cOh, it\u2019s this thing in the catalog, sure.\u201d But they discover new objects all the time, and most of them prove to be totally harmless, just whizzing by through the solar system.<\/p>\n Every now and then, however, one looks a little worrisome. The official threshold for being worrisome is if it\u2019s somewhere between 50 meters [about 164 feet] or greater in size, \u2019cause then it could cause significant damage to Earth if it struck us, and if it\u2019s greater than about a 1 percent chance.<\/p>\n And I keep using some caveats here about how certain we are about this thing striking us because this is not a settled story. This is still so fresh that we don\u2019t actually have this object\u2019s orbit totally refined. We\u2019re still getting more information about it. We\u2019re still observing this thing and trying to figure out what exactly it\u2019s going to be doing, where exactly it\u2019s going in space.<\/p>\n Late last month, when our story about this published, the odds of it striking were about 1.6 percent. And then, in the following couple of days, they rose to 1.7 percent. About three or four days after the story dropped the odds have gone back down to 1.4 percent [laughs]. So, you can see, it\u2019s very active and fluid, but the upshot essentially is that if it stays above 1 percent, then folks should be worried about it.<\/p>\n Feltman:<\/b>\u00a0As you said, we see lots of objects that we never end up having to worry about. How unusual is it to get something above that 1 percent threshold?<\/p>\n Billings:<\/b>\u00a0The last time this happened was about 20 years ago …<\/p>\n Feltman:<\/b>\u00a0Okay!<\/p>\n Billings:<\/b>\u00a0With an asteroid that you might have heard about called Apophis, right? And Apophis, for a while, also had a greater than 1 percent chance of striking Earth, and it made big headlines, and people got really worried about it\u2014I think it helped spark Hollywood movies and various space missions …<\/p>\n Feltman:<\/b>\u00a0Mm.<\/p>\n Billings:<\/b>\u00a0To try to deflect asteroids\u2014so it doesn\u2019t happen that often; that\u2019s one reason why it\u2019s newsworthy. But I just wanna emphasize, of course, that typically what does happen with these things is: you\u2019ll see this initial oscillation in the chances of it striking Earth, and then they just fall off a cliff because we refine the orbit, we realize that we\u2019re safe, and that\u2019s that.<\/p>\n Feltman:\u00a0<\/b>Sure.<\/p>\n Billings:<\/b>\u00a0This one\u2019s a little special, though.\u00a0 T he reason why it\u2019s special has to do with what we already know about its orbit and how long it takes to prepare any adequate response to try to prevent disaster.<\/p>\n Essentially, this thing is going to come back to Earth in 2028. We know we\u2019re safe from it then. It\u2019s already headed away from Earth. It\u2019s whizzing away from us in the solar system. It\u2019s going to be too faint to see with telescopes by late April or early May. So we have this window of time in which we can try to pin down the chances of it striking Earth. If we\u00a0don\u2019t<\/i>\u00a0pin it down, there\u2019s really not much we can do until 2028 rolls around. And if 2028 rolls around and this thing comes barreling by the Earth and we look at it and, and we can get a better gauge of its orbit then and we see that it still has the significant chance of striking Earth, that doesn\u2019t give us much time at all …<\/p>\n Feltman:<\/b>\u00a0Mm.<\/p>\n Billings:<\/b>\u00a0Twenty thirty-two is right around the corner from there.<\/p>\n Feltman:<\/b>\u00a0Right.<\/p>\n Billings:<\/b>\u00a0So we\u2019re left with very few options if we find that it\u2019s actually on a collision course. So there is some discussion now that we might have to almost preemptively act and plan and just have our ducks in a row so that we can get something going very quickly if we need to, if we can\u2019t pin this thing down in the next couple months.<\/p>\n Feltman:\u00a0<\/b>What would that kind of prep look like?<\/p>\n Billings:<\/b>\u00a0Well [laughs], that\u2019s a really good question. Officially, there is a body called the Space Mission Planning Advisory Group; they\u2019re associated with the UN. And as luck would have it, they met in early February. So this was already on the books, and they happened to meet, and of course, top of the agenda was this asteroid, 2024 YR4.<\/p>\n They are supposed to coordinate international responses to any asteroid that is greater than 50 meters that bears a greater than 1 percent chance of striking Earth within the next 50 years. And of course, this asteroid still exceeds that threshold right now. But because it\u2019s so marginal, they decided they\u2019re gonna just watch and wait and reevaluate in late April or early May and see where things stand then. But the idea is that\u00a0they<\/i>\u00a0would help coordinate the response. But what, what would that response be?<\/p>\n There\u2019s really only two options. You can\u2019t do anything that ju \u00a0 st really, really, really gently nudges her out of the way\u2014you have to be a little more violent. You can\u2019t do something like paint one side of the asteroid white and cause its reflectivity to change, which nudges the orbit. You can\u2019t park a spacecraft around it to just orbit around it and use a gravitational-tractor effect, is what it\u2019s called, to gently nudge it out of the way over time. That takes at least 10 years. Instead, you have to hit it. You can either hit it with a kinetic impactor, like NASA did with the DART mission back in 2022 with a different asteroid, and change its orbit. Or you have to nuke it.<\/p>\n Feltman:<\/b>\u00a0Mm.<\/p>\n Billings:<\/b>\u00a0And for an object of this size we\u2019re probably talking about something like a one-megaton hydrogen bomb being blown up right next to it, and that would essentially vaporize it or maybe create a rocket effect from vaporizing so much of its surface that it pushes it into a different orbit.<\/p>\n Feltman:<\/b>\u00a0Obviously, there would be a lot of moving parts to [laughs] a plan like that, so it makes sense that they would wanna start getting their ducks in a row soon. In the unlikely event that this asteroid did impact Earth, what are the sort of best- and worst-case scenarios?<\/p>\n Billings:\u00a0<\/b>Ooh, wow! So there\u2019s preliminary evidence\u2014I, I don\u2019t know how definitive it is\u2014that this rock is, again, between about 40 and 100 meters [about 131 to 328 feet] in size. What\u2019s it made out of? That makes a big difference. Is it stony, or is it metallic?\u00a0<\/b>Is it a big hunk of iron, or is it mostly crumbly carbonaceous s tuff? It seems like it\u2019s stony. It doesn\u2019t seem like it\u2019s metallic. And that changes how it affects the impact process and what it does. If it was, if it was metallic, it would probably manage to pierce through our atmosphere and strike the surface\u2014bad in all kinds of ways. Assuming it\u2019s stony, it will probably break up in the upper atmosphere. That\u2019s still not\u00a0great<\/i>. That, that\u2019s basically like an airburst happening of probably about 10 meg\u2014megatons or so \u2026<\/p>\n Feltman:<\/b>\u00a0Wow, yeah.<\/p>\n Billings:<\/b>\u00a0If this thing\u2019s on the order of 100 meters in size. That\u2019s about the same size as the so-called Tunguska impactor, the unknown object\u2014we don\u2019t know exactly what it was\u2014that came in over Siberia back in 1908 and flattened a huge forest, just knocked all the trees down. Real bad news.\u00a0 I think a lot of reindeer had a really bad time but hopefully not too many people. But it would be that kind of thing. And we\u2019re looking at a swath of the planet that really encompasses a huge number of major population centers, everywhere from parts of South America to South Asia, parts of India, Africa. If you look at it on a globe, you\u2019re like, \u201cOh, yeah, that\u2019s pretty substantial.\u201d<\/p>\n Feltman:<\/b>\u00a0Mm.<\/p>\n Billings:<\/b>\u00a0Now, of course, that region could shrink …<\/p>\n Feltman:<\/b>\u00a0Mm-hmm.<\/p>\n Billings:<\/b>\u00a0And will shrink over time, if it\u2019s even gonna impact anyway.<\/p>\n Feltman:<\/b>\u00a0And of course, as frightening as it is to think about it hitting a major population center, the statistical likelihood is that it would probably be in the middle of an ocean …<\/p>\n Billings:<\/b>\u00a0The ocean, yeah.<\/p>\n Feltman:<\/b>\u00a0With nobody around.<\/p>\n Billings:<\/b>\u00a0Yeah, exactly. I mean, you just look at the basic math of it: most of the swath is still gonna be barren, borderline uninhabited.<\/p>\n Feltman:<\/b>\u00a0So for folks really tuned in to this story, you mentioned April, you mentioned 2028, but when should people expect to know more about this object?<\/p>\n Billings:<\/b>\u00a0Oof, that\u2019s tough to say. I think the best way to put it is: if we don\u2019t know by late April, early May, if we don\u2019t know by th\u00a0 \u00a0 e time it fades from view in our telescopes,\u00a0that\u2019s<\/i>\u00a0when we know, \u201cOh, wow, we really have to start worrying seriously about this thing.\u201d There could be an observation that comes in tomorrow. And when I say observation it\u2019s important to note that it’s not just people gathering fresh data from the skies with telescopes; it can also be people finding an instance of this object in some catalog, some archival data. The more data points you get, the more you\u2019re able to refine its orbit exactly, all the different parameters of it, and then arrive at certainty, but we\u2019re not there yet. It could happen tomorrow; it could not happen for months.<\/p>\n Feltman:<\/b>\u00a0Lee, thanks so much for coming on and talking to us about this asteroid.<\/p>\n Billings:<\/b>\u00a0My pleasure. Let\u2019s try to stay safe.<\/p>\n Feltman:\u00a0<\/b>Like I said at the top of our show, the current estimated risk of collision is 2 percent\u2014or it is at the time of this recording on February 11, anyway. Maybe by the time you\u2019re listening, we\u2019ll have a slightly lower or higher chance of collision. You can find\u00a0updated figures<\/a>\u00a0on the European Space Agency\u2019s website. Also, just as a quick FYI, \u00a0 on February 10,\u00a0the ESA announced in a blog post<\/a>\u00a0that astronomers will use the James Webb Space Telescope to get a more precise estimate of the asteroid\u2019s size a\u00a0 nd orbit. Those observations will take place in March and May.<\/p>\n We\u2019ll keep you posted on the comings and goings of this cosmic interloper as the year goes on.<\/p>\n That\u2019s all for today\u2019s episode. We\u2019ll be back on Friday with a special Valentine\u2019s Day chat all about the importance of significant others\u2014but probably not the ones you\u2019re thinking of.<\/p>\n Science Quickly<\/i>\u00a0is produced by me, Rachel Feltman, along with Fonda Mwangi, Kelso Harper, Madison Goldberg, Naeem Amarsy and Jeff DelViscio. This episode was reported and co-hosted by Lee Billlings. Shayna Posses and Aaron Shattuck fact-check our show. Our theme music was composed by Dominic Smith. Subscribe to\u00a0Scientific American<\/i> for more up-to-date and in-depth science news.<\/p>\n